The short version
Many parasites can infect the digestive system of dogs (see table: Gastrointestinal Parasites of Dogs). The most common ones are described below. Some gastrointestinal parasites of dogs can also cause disease in people (see table: Gastrointestinal Parasites of Dogs and Cats That Also Infect People).
Gastrointestinal Parasites of Dogs
Dogs eat intermediate host (dung beetle) or transport host (chickens, reptiles, rodents)
Most show no signs. When present, signs include weight loss, coughing, and trouble breathing. When severe, dog has difficulty swallowing and may vomit repeatedly after trying to eat. Occasionally, death from rupture of aorta damaged by worms. Diagnosed by microscopic fecal examination, endoscopy, and x-rays.
In areas where the worm is common (southern US, tropics), dogs should be prevented from eating dung beetles, frogs, mice, lizards, or other small animals, and not fed raw chicken scraps.
Gastrointestinal Parasites of Dogs and Cats That Also Infect People
Caution should be exercised in handling infected dogs. Disease is more likely to be severe if the person has a weakened immune system.
Most infected people show no symptoms, but fever, a persistent increase in eosinophils, and an enlarged liver (sometimes with lung involvement) may occur. These signs result from a condition known as visceral larva migrans, which occurs when roundworm larvae migrate through different organs. Rarely, a larva may settle in the retina of the eye and impair vision, resulting in a condition known as ocular larva migrans. Because the eggs adhere to many surfaces and become mixed in soil and dust, strict hygiene should be observed by people (especially children) exposed to potentially contaminated animals or areas. The risk of infection is greater if puppies or kittens are in the environment.
Hookworms (Ancylostoma braziliense; less of an issue with A. caninum, A. tubaeforme and Uncinaria stenocephala)
Roundworms
The large roundworms known as ascarids are common in dogs, especially in puppies. The most important species is Toxocara canis, not only because its larvae may migrate in people, but also because infections are common. Fatal infections may occasionally be seen in young pups. Toxascaris leonina is typically much less common and is generally seen in older dogs.
In puppies, infection with Toxocara canis usually occurs by transfer into the developing fetus through the placenta. The worms can be found in the intestines of the puppies as early as 1 week after birth. Pups may also be infected while nursing. If pups less than 3 months old eat the eggs that have been in the environment for at least 4 weeks, the eggs hatch, releasing larvae that penetrate the intestinal wall. The larvae migrate through the liver, reach the lungs via the bloodstream, are coughed up, swallowed, and mature to egg-producing adults in the small intestine. Many larvae will be carried by the bloodstream to other parts of the dog’s body and remain in the tissues of the dog for years in an inactive form. If immune system suppression occurs, these larvae can become active.
Normally, adult dogs have some resistance to infection. However, during the period around the birth of a litter, the immunity of the female dog to infection is partially suppressed, and the inactive larvae become active, crossing the placenta to the pups and sequestering in the mammary tissue, where they are transmitted in the colostrum and milk. Due to immune system suppression at the time of whelping, active infections may occur in the pregnant dog, with substantial numbers of eggs passed in the feces.
Hookworms
Several types of hookworms can cause disease in dogs. Ancylostoma caninum is the principal cause of canine hookworm disease in most tropical and subtropical areas of the world. Ancylostoma braziliense infects dogs and is sparsely distributed from Florida to North Carolina and along the Gulf Coast in the United States. It is also found in Central and South America and Africa. Uncinaria stenocephala is the principal canine hookworm in cooler regions. It is the primary canine hookworm in Canada and the northern fringe of the United States, but it is found with frequency across the country.
Hookworm eggs are first passed in the feces 15 to 20 days after infection. They hatch in 1 to 3 days when deposited on warm, moist soil. Transmission may result when larvae are ingested or, in the case of A. caninum, from the colostrum or milk of infected dogs. Infections with Ancylostoma species can also result from larval invasion through the skin. Skin penetration in young pups is followed by migration of the larvae through the blood to the lungs, where they are coughed up and swallowed to mature in the small intestine. However, in animals more than 3 months old, larvae may remain in the body tissues in a state of arrested development. These larvae are activated after removal of adult worms from the intestine or during pregnancy, when they accumulate in the small intestine or mammary glands of the mother.
Anemia in young puppies is the characteristic, and often fatal, sign of Ancylostoma caninum hookworm infection. The anemia is the result of the bloodsucking and the bleeding internal wounds that occur when these hookworms shift their internal feeding sites in the small intestine, leaving open wounds in their wake. Surviving puppies develop some immunity and show less severe signs. Nevertheless, malnourished and weakened animals may continue to grow poorly and suffer from longterm anemia. Mature, well-nourished dogs may harbor a few worms without showing signs; these dogs are often the direct or indirect source of infection for pups. Diarrhea with dark, tarry feces accompanies severe infections. Anemia, loss of appetite, weight loss, and weakness develop in longterm disease. Pneumonia may occur in pups with overwhelming infections, making breathing difficult.
Whipworms
Adult whipworms (Trichuris vulpis) in dogs are typically found in the colon and cecum, a part of the large intestine. They attach themselves firmly to the intestinal wall. Eggs are passed in the feces and become infective in about 4 to 8 weeks. Under ideal conditions, whipworm eggs can remain dormant in the environment for several years, unless they become dried out. Once infective eggs are ingested, larvae develop in the small intestine and then move to the cecum and colon, where the adults mature.
No signs are seen in light infections, but as the number of worms increases the cecum and colon can become inflamed, which can cause diarrhea and weight loss. Fresh blood might be seen in the feces in heavy infections and anemia may also result.
Because whipworm eggs take a month to become infective, whipworms can be controlled with good sanitation. Prompt removal and proper disposal of feces is critical. Whipworms are susceptible to drying; therefore, keeping the dog in an environment that is clean and dry reduces the risk of infection considerably. For this reason, kenneled dogs should be maintained on concrete slabs, and never on dirt. A variety of medications—including some monthly drugs that prevent infections with other parasites like heartworms—are available for treating whipworm infections. Your veterinarian will choose one that is appropriate for your dog.
Frequently asked questions
Gastrointestinal parasites dogs?
The Merck Veterinary Manual covers this in the article linked on this page. Many parasites can infect the digestive system of dogs (see table: Gastrointestinal Parasites of Dogs). The most common ones are described below. Som… If your dog is unwell, contact your veterinarian — this page is educational, not a diagnosis.
Gi parasites dogs?
The Merck Veterinary Manual covers this in the article linked on this page. Many parasites can infect the digestive system of dogs (see table: Gastrointestinal Parasites of Dogs). The most common ones are described below. Som… If your dog is unwell, contact your veterinarian — this page is educational, not a diagnosis.
Intestinal parasites dogs?
The Merck Veterinary Manual covers this in the article linked on this page. Many parasites can infect the digestive system of dogs (see table: Gastrointestinal Parasites of Dogs). The most common ones are described below. Som… If your dog is unwell, contact your veterinarian — this page is educational, not a diagnosis.